ALT179_Owners_Manual_Complete

ALT179

T

Toro Micro-Irrigation Owners Manual

toromicroirrigation.com

Written by Inge BisconerToro Micro-IrrigationEl Cajon, CA

First Edition January 2010 2010 The Toro Company

ACKNOWLEDGEMENTS

The author wishes to thank the many members of Toros sales, marketing, engineering, illustration and management staff for their invaluable assistance in creating this document.

toromicroirrigation.com

Toro Micro-IrrigationOwners Manual

234

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Drip Irrigation System Overview

Starting Up Your System

Basic System Operation

Fertigation and Chemigation

Salinity Management

System Maintenance

Maximizing Your Investment

References/Acknowledgements

Appendix

System Information

2CHAPTER 1: Drip Irrigation System Overview | Subsection

2010 The Toro Company

Introduction ..................................................... 3

1 Drip Irrigation System Overview .............. 6

1.1 System Design .................................................... 71.2 Important Tips for System Components ............ 8

2 Starting Up Your System ......................... 14

2.1 Flush, Pressurize, Test and Adjust the System ... 152.2 Connect Lateral Lines to Submains .................. 162.3 Test System Operation and Backfill Trenches ... 192.4 Establish Baseline Readings ..............................20

3 Basic System Operation ...........................24

3.1 Monitor Key Operating Parameters ..................253.2 Irrigation Scheduling ........................................ 28 A. Using the Water Balance Method ................30 B. Additional Considerations ............................40 C. Monitoring Equipment ................................ 47 D. Run-Time Calculators for Permanent

and Row Crops ............................................ 49

4 Fertigation and Chemigation ................. 52

4.1 Plant/Soil/Water Relationships .......................... 53 A. Water Analysis and Interpretation ................54 B. Soil Analysis and Interpretation ....................58 C. Plant Analysis and Interpretation .................. 61

4.2 General Chemical Injection Guidelines ............ 624.3 Chemical Injection Equipment .........................664.4 Chemical Injection Formulas ............................68

5 Salinity Management ..............................72

6 System Maintenance ............................... 76

6.1 Apply Chemicals .............................................. 786.2 Flush the System .............................................. 816.3 Control Pests .................................................... 836.4 Service the Filtration System ............................856.5 Service the Accessory Equipment .....................866.6 Winterize the System ........................................866.7 Startup Procedures ...........................................86

7 Maximizing Your Investment .................88

R References/Acknowledgements .............94

A Appendix .................................................98

CIMIS Evapotranspiration ............................... 100 Sedimentation Test/Determine Soil Texture ... 101

Conversion Factors ......................................... 105 Blank Worksheets ........................................... 109

S System Information ............................... 114

Table of Contents

3Congratulations!You have installed the most advanced method of irrigation known, a quality drip irrigation system from Toro. The drip system youve installed is an excellent investment. In fact, it can be the essential factor that integrates your crop, soil, nutrients and water for optimal results. This manual will help you take full advantage of the precise, efficient, and practical benefits of a drip irrigation system, so it will deliver the most value. Properly operated and maintained, a drip system will pay for itself quickly and last for many years.

Long-Term Benefits

Intelligent irrigation is the precise, efficient and practical method of delivering water to crops that allows growers to maximize profitability and minimize the use of resources. With drip, many growers have successfully increased crop yield and/or quality to increase income, while at the same time reduced the costs of water, fertilizer, energy, labor, weed control, chemical applications, equipment usage and insurance.

This increase in income and reduction of costs often offsets the irrigation equipment investment quickly, thus allowing growers to enjoy higher profitability with the investment in drip irrigation. Field accessibility is often improved, too, along with the ability to farm odd-shaped fields. In most cases, the environmental problems associated with irrigation water runoff, deep percolation, evaporation or wind drift are substantially reduced or eliminated, and wildlife may be enhanced since habitat is not routinely flooded. Whatever the motivation, drip irrigation offers numerous benefits and warrants a commitment to proper operation and maintenance.

Drip Is Different

Drip is different from sprinkler and gravity irrigation, and should be managed differently to maximize its benefits and avoid problems. For instance, drip irrigation is typically used to maintain moisture, whereas sprinkler and gravity irrigation may be used to replace depleted moisture. The chart on the facing page summarizes the main differences.

TORO MICRO-IRRIgATIOn OwnERS MAnuAL

Learn how drip isdifferent to ease the learning curve.

4InTRODuCTIOn

Comparing Drip, Sprinkler and Gravity Irrigation SystemsComparing Drip, Sprinkler and Gravity Irrigation Systems

System Attribute Drip Sprinkler Gravity

Emission device flow rate GPH GPM N/A

Operating pressure 460 psi 3090 psi Low

Duration of irrigation Secs, Mins, or Hrs Minutes Hours, Days

Frequency of irrigation Daily Weekly Monthly

Level of filtration required 120200 mesh 2080 mesh None

Wetting patterns 0.540 feet 5100 feet Broadcast

System application rates Excellent (lowmed) Moderate (medium) Poor (high)

Typical system uniformity Excellent Moderate Poor

Ability to avoid wettingnon-targeted areas Excellent Poor Poor

Ability to avoid weed germination and irrigation Excellent Poor Poor

Ability to avoid runo, deeppercolation, and wind drift Excellent Moderate Poor

Ability to avoid foliage wettingand increased humidity associated with diseases Excellent Poor Poor

Ability to automate the delivery of water and nutrients Excellent Poor Poor

Ability to spoon feed nutrientsvia fertigation Excellent Poor Poor

Ability to reduce irrigation and weed control labor costs Excellent Excellent Moderate Poor

Ability to reduce energy costs Moderate Poor Moderate

Ability to allow field access during irrigation Excellent Poor Poor

Ability to avoid insurance costs Excellent Poor Excellent


1DRIP IRRIgATIOn SySTEM OvERvIEw1.1 System Design1.2 Important Tips for System Components Water Source, Pump, Backflow Prevention, Filtration System, Chemigation System, Flow Meters and Pressure Gauges, Control Valves, Air/Vacuum Relief Valves, Automation Equipment, Pipelines and Fittings, Emission Devices

7 TORO MICRO-IRRIgATIOn OwnERS MAnuAL

1.1 System DesignDesigning a drip irrigation system can be complex. Toro Irrigations companion document, The Micro-Irrigation Design Manual, covers all aspects of design (including plant/soil/water relationships, water treatment, hydraulic theory and pumps) as well as some information regarding installation, operation and maintenance. Below is a summary of important issues that should have been considered during the design and selection process.

Its best to review these issues with the design engineer before and after system design, installation and purchase to ensure that the system operates properly and performs to your expectations.

Review your system with the designer, both before and after your purchase.

System Uniformity

Water Analysis

Soil Analysis

Crop Information

Pump Test

Site Information

Labor

Expansion

Maintenance

Automation

Monitoring

Drip Irrigation System Design Stage Checklist Drip Irrigation System Design Stage Checklist

System Life Expected system life will influence the type and quality of system components. Systems may last well over 10 or even 20 years if high quality and well maintained.

Expected irrigation uniformity will also influence the type and quality of system components. Drip systems routinely operate at over 90% uniformity if high-quality components are chosen and well maintained.

Find out whats in the water before the system is designed and built. Water quality will dictate filtration, emission device selec-tion and chemigation, and may change seasonally or with heavy pumping.

Find out the soil type such that an emission device with the right flow rate, spacing and application rate may be chosen, and so that any soil physical or chemical problems may be addressed at the design stage.

The designer should know the cost and quantity of water and fertilizer that will be needed to grow the crop(s), as well as the cultural practices and planting dimensions.

If a pump is already present, get a pump performance curve to make sure it runs efficiently at the desired flow and pressure.

The designer should have access to topographic, weather, water, fuel, and other infrastructure information.

Cost and availability of labor is an important element of equipment selection and decisions regarding automation.

Small adjustments in the current design will ease future system expansions, if any.

The designer should make provisions for the safe and effective injection of all chemicals that will be used including fertilizers, acid and chlorine. In addition, the designer should ensure the system may be properly flushed.

If system automation is desired initially, or even later, it should be known at the time of design.

Basic flow and pressure monitoring equipment should always be specified. If additional soil, weather or plant monitoring equipment will be used, integration with the irrigation control equipment should be considered.

8 2010 The Toro Company

CHAPTER 1: Drip Irrigation System Overview | 1.2 System Components

1.2 Important Tips for System ComponentsDrip irrigation systems are unique because much of the system is buried. As the Typical Drip System Layout illustration shows, the water sources, pumps, filters, chemical injection equipment and controls are clearly visible, while little of the field portion of the system is seen. This is true for field crop sub-surface drip irrigation (SDI), short-term vegetable crop, longer-term vegetable crop, vineyard and orchard irrigation. Heres what you need to know about the principal components, along with a brief description of each components role in the system. Your system probably has many of these components.

water Source

water quality influences many aspects of irrigation including filtration, wetting patterns, fertilizer compatibility and plant growth. Although clean, potable water supplied by a water district is occasionally used to irrigate crops, irrigation water is more likely to come from a surface river, stream, lake or canal, or from the groundwater by drilling a well. Depending on the water quality, a reservoir or a screen, disc and/or

sand media filtration system must be used to remove sand, algae and other contaminants that could clog the drip irrigation system. If certain minerals are present, or if the pH isnt right, chemical treatment may be required as well. Even if you didnt obtain a Water Quality Analysis prior to installing the system, its never too late. Obtaining one will provide immediate help with important drip irrigation management decisions. See Chapter 4 for more about water testing and analysis.

Know whats inyour water and how conditions may change during the course of the season.

Typical Drip System Layout

Control Valves

Primary FiltersIrrigation Controller

Well Pump

Chemical Injection Tanksand Equipment

Surface Reservoirand Pump

Air/VacuumRelief Valves

Aqua-Traxx Drip Tape SDI (Subsurface)

Copyright 2008, The Toro Company

Aqua-Traxx and Oval Hose Hose and Emitters Dripline


Pump

Make sure your pump is adequate and efficient for the flow and pressure conditions. Unless water is pressurized at the source, a pump will be needed to push water through the pipes and emission devices. Vertical turbine pumps are typically used on wells, and centrifugal pumps are used for surface water supplies. Obtain a performance curve for your pump and have changes made if it isnt right the energy savings alone will easily pay for any upgrades you might have to make, which will also improve system operation and, ultimately, crop production.

Backflow Prevention

Prevent irrigation water and/or chemicals from accidentally contaminating the water supply with a backflow prevention device. The many different backflow prevention system types may include flow sensors and interlocking electrical connections that shut down both the irrigation and chemigation pump should a failure in either system occur. This prevents chemicals from entering the water source as well as from entering the irrigation system when it is not operating properly.

Filtration System

good filtration is essential for proper system operation and long-term performance. Filters are commonly used to remove sand, silt, precipitated minerals and organic matter so that irrigation water will

not clog the emission devices. Water quality and emission device specifications will determine the filtration type, level and quantity, but most drip systems require from 120200 mesh filtration. Irrigation filters will NOT remove salt, dissolved solids or other toxic elements, nor will they adjust the water pH. Even if potable water is used, a basic screen filter is still required to remove sand and minerals. For good filtration, filters must be backflushed when they become dirty.

Chemigation System

If you use a chemigation system, make sure the injected chemical will not clog or otherwise damage the irrigation system. Prior to chemigation, a simple jar test should be conducted and/or a compatibility chart consulted. Chemical injectors deliver nutrients to the plants with the water and also apply system maintenance chemicals such as acid, chlorine or other line cleaners. Some systems use a separate pump, and others use a venturi-type device that uses a pressure differential in the circuit to create suction pressure in tubes connected to the chemical tanks. See Chapter 4 for jar test instructions.

Flow Meters and Pressure gauges

Make sure your system has a flow meter and pressure gauges that work! Although simple and relatively inexpensive, these gauges are often overlooked or not maintained. These monitoring devices are essential to proper system operation. System flow rate helps detect leaks or clogging, and must be known to determine the application rate for irrigation scheduling purposes. System pressure also helps detect leaks or clogging, and is essential for managing filters, chemical injectors and the system operating window.

It takes 27,154 gallons of water to equal one acre-inch of water, so pumping efficiency is essential for energy savings.

Backflushing the filters is crucial to system performance.

Backflow prevention is important, recommended and in some areasrequired by law.

10



Control valves

Control valves must be properly set to achieve proper system flow and pressure. Sometimes simple ball or butterfly valves are used, but often the system uses sophisticated flow and pressure regulating valves. Larger valves control flow from the pump to the filters and then to the field, and sometimes a valve will reduce field flow to enhance filter backflush. Zone valves control which blocks receive water, and flush valves at the ends of all system pipelines allow the system to be purged of impurities. Although valves are typically operated by hand, many are now automated.

Air/vacuum Relief (AvR) valves

AvR valves help prevent negative suction pressure, which can cause serious clogging problems especially if laterals are buried or in constant contact with settled soil. AVR valves are commonly installed at high points and at the end of irrigation pipelines including supply lines, mainlines, submains and control risers to let air escape when pipelines are filling, to allow air to enter when pipelines are draining, to remove air pockets at system high points caused by entrained or dissolved air, and to

prevent negative suction pressure in laterals after system shutdown. In most cases, clogging from vacuum suction may be prevented by properly installing vacuum relief valves on the lateral inlet, high point and outlet submains, or by installing flush valves at the end of each lateral for vacuum relief.

Automation Equipment

Automation equipment consisting of controllers, valves and/or sensors can help maximize drip irrigation system benefits. Many systems incorporate a controller that communicates with valves and sensors via wires or via wireless devices. The user typically programs the controller to turn valves on and off at desired times. Since most controllers allow sensor input as well, systems may also be automated according to weather, soil or system conditions. Note that systems capable of automation may also be operated manually.

Pipelines and Fittings

Its important that all pipelines and fittings are properly sized to withstand maximum operating pressures and convey water without excessive pressure loss or gain. Pipelines carry water from the pump to the filters, valves and emission devices. PVC pipe may be used throughout the system or combined with steel at the pump station, flexible PVC or polyethylene (PE) layflat for submains, and polyethylene hose or drip tape for laterals. Be sure to consider the expansion and contraction that occurs under normal outdoor operating conditions, and make sure pipelines are properly secured, thrustblocked and connected to one another with welds, glue or friction fittings. PVC pipe and fittings should be cleaned, deburred and primed before gluing. Because much of the pipeline is buried and difficult to access and repair, especially after crop growth, making sure fittings are secure at installation can save significant repair issues later.

Negative suction pressure can cause serious clogging problems.

Prevent potential crop damage from a system shutdown by pressure-testing pipelines early.


Emission Devices

Emission devices must be selected and installed with the utmost care because problems are difficult to solve solving problems is difficult since there are literally hundreds or thousands of emission devices in a typical system. Emission devices deliver water and nutrients directly to the plant root zone as shown in the illustration below. Drip tape and dripline will have built-in emission devices, and polyethylene hose will have emitters, jets or micro-sprinklers attached. Quality is essential, since a typical drip system includes hundreds or even thousands of emission devices. Each device should be durable, resistant to clogging, and emit the same amount of water even under variable pressures. In addition to quality, the flow rate and spacing of the emission device is important in determining the wetting pattern as well as the likelihood of having runoff or deep percolation problems. The illustration below (Mikkelsen, 2009) shows how a well managed drip system provides water and nutrients to the crop rootzone without runoff or deep percolation. Emission devices of poor quality may require more maintenance, not provide optimum irrigation efficiency, and need replacement far earlier than a quality device. Simply put, this is no area to try to cut costs quality is essential. At a minimum, emission devices should have a low manufacturing coefficient of variation (CV), the irrigation system should have a high design Emission Uniformity (EU), and all components should have a good warranty, backed by a company that can be trusted.

N P K

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Main Toro Components


Booster Pump

Flow

Flow

Aqua-Traxx with the PBX Advantage

Aqua-Traxx PC Premium Drip Tape

Drip In Classic and Drip In PC Dripline

BlueLine PC Dripline

Blue Stripe Hose Blue Stripe Oval Hose Layflat Discharge Hose Pro-Loc (pictured), Poux, XPando, Loc-Eze and Ring-Loc Fittings

Turbo-key, Turbo-SC Plus, NGE SF, NGE AL (pictured), and E2 Online Emitters

MC-E Series Irrigation Controller

Junior MAX Irrigation Controller

Micro-Sprinkler VI Classic and Micro-Sprinkler VI PC

Mazzei Injectors XD Filters and F Series Plastic Filters

Bermad Valves Toro and Irritrol (pictured) Valves

2STARTIng uP yOuR SySTEM2.1 Flush, Pressurize, Test and Adjust the System2.2 Connect Lateral Lines to Submains2.3 Test System Operation and Backfill Trenches2.4 Establish Baseline Readings


Starting up your SystemProperly designed, installed, operated and maintained drip irrigation systems may last indefinitely. However, drip systems are vulnerable to over-pressurization and clogging, both of which can drastically reduce the systems life and performance. The following step-by-step guide shows how the system should be initially pressurized and tuned, and how it should be routinely operated and monitored for optimal performance. Note: It is assumed that the system has been completely installed and pipelines have been partially backfilled, but that lateral lines have NOT been connected to the submains yet.

2.1 Flush, Pressurize, Test and Adjust the System

a. Open all control and flush valves.

b. Close all submain control valves.

c. Turn on the pump and slowly fill and flush the mainlines, allowing air to exit the system through the air-relief valves. If necessary, divert the flush water from the flush valves.

d. Once the mainlines have been thoroughly flushed, close the mainline flush valves and bring the mainline up to test pressure.

e. Maintain test pressure for 24 hours. If leaks develop in the mainline, immediately shut off the system, repair leaks, flush the mainline again, and repeat the pressure test.

f. After the mainline has been flushed and passes the pressure test, flush the submains until clean by opening the submain control and flush valves. Again, divert the submain flush water if necessary.

g. After the submains are thoroughly flushed, adjust the submain block control valves so that downstream pressure will not exceed the maximum pressure rating of the lateral lines that will be connected after the flush valves are closed. Thin-walled tape products may have a maximum pressure rating of 10 psi, while thick-walled polyethylene hose or dripline products typically withstand 50 psi or more.

h. While the submains are flushing, make sure the filters are working properly, and that they have been thoroughly backflushed.

If a backflush controller is used, set the pressure differential point at which the filter will automatically backflush. Depending on the filter make and model, inlet and outlet pressures should differ about 2-3 psi when the filters are clean, and about 10 psi when the filters are dirty and should be backflushed. If a

controller is not being used, these gauges must be monitored often so that manual backflush is performed before the filters become fouled. Variables in gauge readings and elevation differences should be taken into account. Remember that 2.31 feet of elevation equals 1 psi.

The valve controlling the volume of flush water exiting the sand media filter drain line during backflush must be carefully set. The valve must maintain enough backpressure on the filters during backflush to prevent sand from exiting the filter tanks. At the same time, the valve must allow enough

volume to exit the filters so that the sand bed is adequately lifted and cleansed. The valve is set properly when minute quantities of sand begin to appear in the flush water.

i. After the submain block valves and filter valves have been properly set, close the submain flush valves and pressurize the submain to test pressure for a period of time. If there are leaks, shut the system off, make repairs, and repeat the pressure test.

Pressure testingis essential!

Automatingthe backflushfunction is highlyrecommended.

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CHAPTER 2: Starting up your System | 2.2 Connect Lateral Lines to Submains

2.2 Connect Lateral Lines to Submains

a. After the submains have been successfully flushed and pressure tested, open the submain flush valves and the ends of all lateral lines for flushing after connection. If the lateral lines are plumbed into a flushing submain, open the flushing submain flush valves.

b. Connect the lateral lines to the submain, and flush the lateral lines until clean. If necessary, close the submain flush valves to achieve adequate flushing volume on the laterals.

c. After the lateral lines have been flushed clean, close all submain and lateral flush valves and allow the system to stabilize at operating pressure.

d. Re-adjust all submain block valves as necessary to conform to design pressure specifications, taking care to not exceed the maximum pressure rating of the lateral lines.

Its extremely important that the laterals are connected properly to the submains to prevent leaks, kinking or clogging. Holes must be drilled correctly with care taken to remove shavings and burrs. Also note the variety of lateral end connections that are available to help facilitate flushing, whether automatically or manually. Although end-of-line flush valves or flushing submains are more costly, they greatly enhance the irrigators ability to easily flush laterals manually as opposed to closing each lateral with a figure 8, a threaded cap, a valve or, in the case of tape, tying a knot.

The following pictures show actual field applications.

Dont over-pressurize orclog emissiondevices.


The following illustrations show how tape, hose or dripline laterals may be connected to polyethylene oval hose, flexible PVC layflat, or rigid PVC supply or flushing submains. The initial cost of some options are more expensive than others, but in exchange enhanced performance, durability and longevity are delivered. Since some operations such as lateral flushing may occur frequently, the cost of operational labor must be factored into the connection type decision as well.

Flexible Polyethylene Oval Hose

The six illustrations below show how oval hose is punched and then connected to tape laterals via spaghetti tubing or barbed connectors of various sizes. Note that the bottom left illustration shows Toros Pro-Loc fitting with a valve option that facilitates control of individual laterals from the oval hose submain.

Flexible PvC Layflat

This submain material is very popular because it collapses easily for portability. A more secure tear-drop shaped fitting may be used to connect the layflat to the tape laterals as shown in the first four illustrations below. In addition, as with oval hose, spaghetti tubing may be inserted into a hole as well.

18


Rigid PvC Pipe

Rigid PVC is typically used to connect laterals in permanent crops and in subsurface drip irrigation systems. Since the pipeline is usually buried, it is important that the fittings are reliably secure and that transition tubing does not bend or crimp to obstruct water flow. Toros Xpando Take-Off and Pro-Loc fittings are the perfect solution, providing transitions from PVC pipe to polyethylene transition tubing, and transitions from polyethylene tubing to drip tape, hose or dripline laterals.

Lateral Couplings

The following illustrations show how tape and hose/dripline are coupled in the field with Pro-Loc tape and dripline fittings, or with wiretie and blank tubing.

CHAPTER 2: Starting up your System | 2.2 Connect Lateral Lines to Submains


Lateral Ends

Hose, dripline and tape lateral ends may be closed with a variety of fittings including with a Pro-Loc shut-off valve fitting, with a figure-8 fitting (for hose only), with a Pro-Loc flush valve fitting, with a wiretie fitted to rigid hose, or with a napkin ring (tape only).

2.3 Test System Operation and Backfill TrenchesSystem connections, flushing, pressure testing and pressure setting have now been completed. Once youve determined that all underground components, including pipes, fittings, control wires and tubing, are working properly, backfill the trenches. Care must be taken during backfilling to prevent collapse or other damage to the pipe, particularly with large, thin wall pipe. Note that open trenches can pose a danger and should be protected prior to backfilling. In some cases, backfilling prior to pressure checking may be warranted.

20


2.4 Establish Baseline ReadingsBecause significant portions of drip systems are buried and cant be easily viewed, pressure gauges and flow meters are key to diagnosing problems and checking operating status. After the system has been connected, flushed and pressure-tested with control valves properly set and its been verified that all underground components are working properly take the following baseline readings:

Record readings from all pressure and flow gauges, including before and after pumps, filters, main and submain control valves, tape inlets and tape outlets.

Examine the condition of filter flush water to verify that the backflush valve has been properly set.

Examine block tape flush water by capturing water in a jar to make sure a clogging hazard doesnt exist.

These readings should be used to verify that the system conforms to design specifications, and should serve as operational benchmarks in the future. The flow meter reading should also be used to determine and/or verify the application rate for future irrigation scheduling calculations (discussed in Section 3.2).

The following pictures show where some of the readings should be taken.

CHAPTER 2: Starting up your System | 2.4 Establish Baseline Readings


Control Valves


Well Pump








Control Valves


Well Pump







Filter inlet pressure

Block inletBlock outlet

Filter outlet pressure

Compare baselinereadings withdesign specs.


To assist in data collection, the following template may be used:

SDI Baseline Readings Data Collection SheetSDI Baseline Readings Data Collection Sheet

SDI Block Valve Baseline ReadingsSDI Block Valve Baseline Readings SDI Block Valve Baseline ReadingsSDI Block Valve Baseline Readings

System Pump Filter Inlet Filter Outlet Mainline Appearance AppearanceFlow Rate Pressure Pressure Pressure Control Valve of Filter Outlet Block Valve Block Valve Tape Inlet Tape Outlet of Tape Outlet Pressure Flush Water Inlet Pressure Outlet Pressure Pressure Pressure Flush Water400 GPM 40 psi 38 psi 3037 psi 28 psi No sand, clear 1823 psi 15 psi 1214 psi 4 psi Clear after backush

Example: Target value of readingsupplied bydesign engineer:Immediately after purchase:

Week 1Week 2Week 3Week 4Week 5Week 6Week 7Week 8Week 9Week 10Week 11Week 12Week 13

Block Valve #_______




1823 psi 15 psi 1214 psi 4 psi Clear

AppearanceBlock Valve Block Valve Tape Inlet Tape Outlet of TapeInlet Pressure Outlet Pressure Pressure Pressure Flush Water




1823 psi 15 psi 1214 psi 4 psi Clear

AppearanceBlock Valve Block Valve Tape Inlet Tape Outlet of TapeInlet Pressure Outlet Pressure Pressure Pressure Flush Water

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CHAPTER 2: Starting up your System | 2.4 Establish Baseline Readings

when to Take Readings

As a general rule, baseline readings and subsequent monitoring should occur after the system pressure and flow have stabilized. The system should be filled slowly so that air has plenty of time to escape through the air-relief valves and to prevent water hammer on the filters, valves and critical pipe fittings. A manually operated butterfly valve, generally pre-set or automated to facilitate a slow fill, is often placed downstream of the pump prior to the filters to help regulate fill-up flow.

How to Determine Stabilization Time

The following calculations will help you determine how long the system must operate before pressure and flow have stabilized, so the operator knows when readings may be taken. For example, if the area within all pipelines and tape will consume 5,000 gallons of water, and the system flow rate is 500 gpm, then stabilization will occur after about 10 minutes of operation.

1. Calculate the total volume of area within the drip tapes and conveyance pipes in cubic feet. use the following formula:

Pipeline Volume (cubic feet) = 3.14 x D2 /4 x L Note: D = Pipeline Internal Diameter (in feet) and L = Pipeline Length (in feet)

2. Convert this volume to gallons by multiplying by 7.48 gallons per cubic foot.

3. Compare volume with system flow rate. Divide the total volume in gallons (from Step 2) by the gallons per minute (gpm) flow rate to determine how many minutes it will take to fill the pipeline.

Example

200 feet of pipe (L) with an internal diameter of 3.284 inches (D) would have the following internal volume in cubic feet (remember to convert inches to feet):

Pipeline Volume (cubic feet) = 3.14 x (3.284 inches / 12 inches/foot)2 / 4 x 200 feet After converting inches to feet: 3.14 x .27372 / 4 x 200 feetTherefore: 3.14 x .0187 x 200 = 11.74 cubic feet

Since 7.48 gallons occupies one cubic foot of volume, the volume of water in this 200-foot section of pipeline would be: 11.74 cubic feet x 7.48 gallons per cubic foot = 88 gallons. If the system flow rate were 10 gpm, it would take 88 gallons /10 gpm = 8.8 minutes to fill the pipeline.

3BASIC SySTEM OPERATIOn3.1 Monitor Key Operating Parameters3.2 Irrigation Scheduling A. Using the Water Balance Method B. Additional Considerations C. Monitoring Equipment D. Run-Time Calculators for Permanent and Row Crops


Basic System Operation Now that the system has been constructed and is operating properly, its time to irrigate! To protect and maximize your investment, its highly recommended that the system be monitored on a routine basis to ensure proper operation, and that irrigations are scheduled intelligently to avoid waste.

3.1 Monitor Key Operating ParametersOnce the irrigation season is under way, the systems pressures and flows should be monitored, the flush water assessed, and system integrity ensured on a routine basis.

Monitor for Differences in System Pressure and Flow

After the system has stabilized, the systems vital flow and pressure signs should be monitored and compared with the benchmark readings you recorded after initial system startup to make sure the system is operating as designed. Remember, flow and pressure are closely related, so differences from the benchmark readings may indicate:

Wrong control equipment settings or control equipment failure

Clogging of the filters or emission devices from inorganic, organic or mineral precipitants

Leaks from pipe or tape failure, loose fittings, rodent or insect damage

Use the System Troubleshooting Guide shown here to help isolate the problem.

System Troubleshooting GuideSystem Troubleshooting Guide

High Low Low High High Low High Low

SystemFlow Meter:

FILTEROutlet Pressure: High Low Low High

High Low High Low

High Low Low High High Low High Low SystemFlow Meter:

BLOCK VALVE Outlet Pressure:

SystemFlow Meter:

Possible Problem and Solution:


1. Pump valve is opened too wide.

2. Pump output should be decreased.

1. Pump valve should be opened wider.

2. Pump output should be increased.

1. There is a leak in the system.

2. A valve is opened in error.

1. Emission devices or lters are clogged.

2. A valve needs to be opened more.

3. Additional zone valves need to be opened.

4. Correct zone valves need to be opened.

1. Pump valve is opened too wide.


1. Filters are clogged and should be backushed / cleaned.

2. Pump valve should be opened wider.




1. Emission devices are clogged.


3. Additional zone valves need to be opened.

4. Correct zone valves need to be opened.

1. Block valve is opened too wide.


1. Block valve should be opened wider.


3. Filters are clogged and should be backushed.



1. Emission devices are clogged.


PUMPOutlet Pressure:


26


CHAPTER 3: Basic System Operation | 3.1 Monitor Key Operating Parameters

In addition, these hypothetical examples show how pressure and flow rate measurement records may be used to discover and resolve operational problems (Lamm & Rogers, 2009).

Monitor Lateral Flush water Quality

As often as each irrigation, the ends of laterals should be opened and the contents emptied into a jar for visual inspection of water quality. When water quality begins to degrade, as shown by color, grit, organic or any solid materials in the flush water, then system maintenance should be performed. Since the ends of laterals in SDI systems are typically plumbed into a flushing submain as shown in the illustration at the bottom of page 20, the flushing submain valve must be opened and the flush water examined. If this is impractical to perform during each irrigation, another alternative is to install a Tee into the end of a tape lateral with the third leg capped at the surface for easy viewing of lateral flush water on a periodic basis.

The following pictures show how pressure, flow and flush water can be checked.

Troubleshooting Operational Problems with Pressure and FlowrateTroubleshooting Operational Problems with Pressure and Flowrate

590

8

9

10

11

12

600

610

620

630

640

650

660

670

680

690

456789

1110

A

B

C

D

Zone Inlet

June JulyMonth

Pressure

(psi)

Zone

Flowrate (G

PM)

August September

Flushline Outlet

Anomaly A: The irrigator observes an abrupt owrate increase with a small pressure reduction a the Zone inlet and a large pressure reduction at the Flushline outlet. The irrigator checks and nds rodent damage and repairs the dripline.

Anomaly B: The irrigator observes an abrupt owrate reduction with small pressure increases at both the Zone inlet and the Flushline outlet. The irrigator checks and nds an abrupt bacterial are-up in the driplines. He immediately chlorinates and acidies the system to remediate the problem.

Anomaly C: The irrigator observes an abrupt owrate decrease from the last irrigation event with the pressure reductions at both the Zone inlet and Flushline outlet. A quick inspection reveals a large ltration system pressure drop indicating the need for cleaning. Normal owrate and pressures resume after cleaning.

Anomaly D: The irrigator observes a gradual owrate decrease during the last four irrigation events with pressure increases at both the Zone inlet and Flushline outlet. The irrigator checks and nds that the pipelines are slowly clogging. He immediately chemically treats the system to remediate the problem.

Anomaly A: The irrigator observes an abrupt flowrate increase with a small pressure reduction at the Zone inlet and a large pressure reduction at the Flushline outlet. The irrigator checks and finds rodent damage and repairs the dripline.

Anomaly B: The irrigator observes an abrupt flowrate reduction with small pressure increases at both the Zone inlet and the Flushline outlet. The irrigator checks and finds an abrupt bacterial flare-up in the driplines. He immediately chlorinates and acidifies the system to remediate the problem.

Anomaly C: The irrigator observes an abrupt flowrate decrease from the last irrigation event with the pressure reductions at both the Zone inlet and Flushline outlet. A quick inspection reveals a large filtration system pressure drop indicating the need for cleaning. Normal flowrate and pressures resume after cleaning.

Anomaly D: The irrigator observes a gradual flowrate decrease during the last four irrigation events with pressure increases at both the Zone inlet and Flushline outlet. The irrigator checks and finds that the pipelines are slowly clogging. He immediately chemically treats the system to remediate the problem.

From left to right: Pressure gauge on mainline; flow meter; pressure gauge on tape; monitoring tape flush water.


Monitor for Mechanical Damage

Drip tape and polyethylene laterals are also susceptible to mechanical damage from a number of sources, including installation equipment, tillage equipment, insects, birds, rodents, excessive pressure or the lens effect of sunlight when magnified through water beneath clear plastic mulch. Tape injection equipment should be routinely inspected, and the drip system should be inspected for evidence of mechanical damage, indicated by puddles of water, squirting, loss of pressure or crop loss. When such damage occurs, pests must be controlled or managed or equipment adjustments should be made to avoid future problems. The following pictures illustrate the various types of mechanical damage that can occur. Note that sunlight damage from the lens effect is uncommon in SDI applications since the tubing is buried and is not subject to magnification of sunlight under clear mulch. However, SDI systems are especially susceptible to rodent damage since populations are no longer controlled with the previous irrigation or cultural practices.

Examples of Mechanical and Other Damage

Bird Damage Equipment Damage Equipment Damage Excessive Pressure

Insect Damage Insect Damage Insect Damage Lens Effect Damage

Rodent Damage Rodent Damage Rodent Damage Rodent Damage

28


CHAPTER 3: Basic System Operation | 3.2 Irrigation Scheduling

3.2 Irrigation SchedulingIrrigation scheduling is the process of deciding when and for how long to run the irrigation system. Its a complex but important topic because it influences whether the crop gets the right amount of water and nutrients, whether valuable water is wasted to runoff or deep percolation, and whether salts are moved beyond the root zone.

The Hydrologic Cycle illustration (NASA, 2009) demonstrates how complex weather, soil, geography, geology and plant growth influence water movement and use. Irrigation scheduling uses both art and science to balance known facts such as soil type, system application rate and crop species with changing conditions such as weather, chemistry, stage of plant growth and farm cultural operations. On one end of the spectrum, the irrigator may make decisions by physically evaluating the moisture content in a sample of soil or visually monitoring the appearance and color of the crop. On the other hand, sophisticated instruments may be used to collect data on soil moisture, plant water stress, weather conditions and theoretical plant water use.

This figure, Transpiration (Techalive, 2009), shows the process by which plants use water as its taken in through the roots, moves up the stem and then transpirates to the atmosphere. Researchers have generated data on this process for many crops, and its available for growers to use. Software may also be used to interpret this information and generate scheduling recommendations for advanced applications or automated operation.

TRANSpIRATION1. Water is taken in through the root hairs.2. Water moves up the stem through the xylem vessels,

which conduct water and minerals to the leaves.3. Guard cells open, creating a pore through which water

vapor can escape.4. Water vapor escapes through open stoma (singular =

stomata), mainly on the undersides of leaves. (4a. Stomata, 4b. Plant Cell)

1

3

2

4

4a

4b

3


The figure below, Irrigation Schedule Based on Soil Moisture Status (adapted from USBR, 2000, pg. 87) shows two different irrigation scheduling strategies. The first strategy (in purple) employs the use of a drip irrigation system to refill the soil profile frequently, keeping the soil at optimum moisture. The second strategy (in green) refills the profile infrequently, thus allowing approximately 50% of the available soil moisture to become depleted before refilling the profile. This schedule is typical of sprinkler irrigation systems as well as some gravity systems, and may not provide optimum moisture to the crop. Note that

the definition of optimum moisture may change according to crop, stage of growth, quality parameters and other variables, and may include some level of drying down, or deficit irrigation, with any type of irrigation system.

In addition to high frequency irrigation, high frequency fertigation in trials with phosphorus and potassium also has proven higher yield results as shown in the adjacent graph (Lamm, 2007 after Phene et al.,1990).

Drip vs. Typical Irrigation ScheduleDrip vs. Typical Irrigation Schedule

(1) Full soil reservoir(2) Often 50% of available soil capacity(3) Empty soil reservoir

1

2

3

4

Irrigation SeasonIrrigation Season

FallSpring Summer Fall

Saturation PointField Capacity (1)

Rell Point (2)

Wilting Point (3)

Water Holding

Cap

acity (in

./ft.)

Typical IrrigationSchedule

Drip Schedule

Allowable DepletionAvailable Water

Soil Always at OptimumMoisture

The Effect of Irrigation Frequency and Fertigation on Tomato YieldThe Effect of Irrigation Frequency and Fertigation on Tomato Yield

1984 1985 1987

300

75

50

25

0

100

125

250

275

200

225

400

500

600

700

800

Year

ETc (m

m)

Tomato Yield (M

g/ha)

No Injected P or K

High Frequency SDIHigh Frequency DILow Frequency DICrop ET

Injected P and KInjected P

Tomato yield and crop ET as affected by irrigation system type and fertigation of macronutrients phosphorus (P) and potassium (K) on clay loam soil. Tomato yield and crop ET as affected by irrigation system type and

fertigation of macronutrients phosphorus (P) and potassium (K) on a clay loam soil. Data from Phene et al. (1990).

Proper scheduling maximizes profitsand minimizesproblems.

30


CHAPTER 3: Basic System Operation | 3.2-A Irrigation Scheduling Using the Water Balance Method

In short, the irrigation manager must decide when and how long to irrigate to achieve the best results for any given crop and its unique conditions. In this manual, we will discuss the Water Balance Method and then explore additional factors affecting scheduling before creating a typical irrigation schedule based on theoretical conditions.

A. using the water Balance MethodThe Water Balance Method assumes that the crop root zone is a water reservoir, similar to a bank account. As the crop uses water through the process of evapotranspiration (ET), water is withdrawn from the account. This water can then be replaced by rainfall or irrigation deposits. A running balance keeps track of the theoretical water level in the water reservoir, and actual field monitoring verifies the theoretical balance before final irrigation decisions are made.

How to Calculate Run Time and Schedule

At a minimum, you need to know two things to successfully calculate theoretical run time and schedule irrigations using the Water Balance Method: 1) crop water use (to determine daily water withdrawal), and 2) irrigation system net application rate (to determine how much water is applied per hour of irrigation). Both are used to calculate theoretical run time. Reference ET, Crop Coefficient and Crop Coverage Decimal data are readily available from local government and university sources, and we encourage you to use these resources for help.

The irrigation system net application rate should be supplied by the irrigation dealer at the time of purchase, but irrigation system manufacturers, consultants and extension agents can help as well. The following formulas will help calculate Theoretical Run Time, Crop Water Use and Net Application Rate.

EQuATIOn 1 THEORETICAL Run TIME:

Run Time (mins.) = Crop Water Use (inches) / System Net Application Rate (inches/hr.) x 60

Example

If crop water use is .33" per day, and the net application rate of the irrigation system is .08"/hour, how long should the system operate per day to replace crop water use?

Since the systems net application rate typically doesnt change, only crop water use data must be collected on a frequent basis to calculate theoretical run time. However, plant and soil field conditions must also be monitored to verify that the calculated schedule will deliver desired results or for learning how theoretical values must be adjusted.

Equation 1 Theoretical Run Time Per DayEquation 1 Theoretical Run Time Per Day

Crop Water Use Net Application Rate x 60 = Run Time Per DayExample: 0.33 in./day 0.08 in./hour x 60 = 248 minutes/day


The following provides more detailed information regarding the development of crop water use and net application rate information.

Determining Crop water use

Crop water use is typically expressed in inches of water per day as ETc (evapotranspiration of the crop). Its typically calculated by multiplying the reference evapotranspiration (ETo) rate, which is generated from daily local weather station data, by the crop coefficient (Kc), which is unique to the crop and the geography where it is grown. The purpose of the Kc is to adjust generic weather information to reflect the specific crop being grown. Weather and crop coefficient data may be obtained from local government or university sources, or may be generated on the farm with proper equipment and research procedures. The adjacent Monthly Average Reference Evapotranspiration by ETo Zone table (CIMIS, 1999) shows data by month throughout California. The Potato Crop Coefficient vs. Growth Stage graph (AgriMet, 2009) shows how the crop coefficient changes according to Percent Growth Stage (0 = emergence, 100 = row closure, 200 = dead vines). Note how ETo and Kc values both change during the season. See the Appendix for additional ETo and precipitation data.

Theoretical crop water use should also be reduced if the crop doesnt cover 100% of the soil surface. For instance, University of California researchers recommend that if a tree crop provides more than 62% shading, then established crop coefficients should be used. However, if less than 62% of the soil surface is shaded with the tree canopy, then a 2:1 ratio should be used to generate a correction factor. For example, if an immature canopy only shaded 20% of the soil surface, then estimated water use of the immature orchard would be 2 x 20 = 40% as much water as a mature orchard. Thus, a multiplier of .4 should be used. The adjacent graph illustrates how percent of mature ETc varies with percent ground shading (Snyder, UC Leaflet 21259).

Potato Crop Coecient vs. Growth StagePotato Crop Coecient vs. Growth Stage

0.00

Percent Growth Stage

Crop

Coe

cien

t

0.100.200.300.400.500.600.700.800.901.001.101.20

0 50 100 150 200 250

The Eect of Ground Shading on Permanent Crop ETcThe Eect of Ground Shading on Permanent Crop ETc

0 10 20 30 40 50 60 70 80 90 100

100

90

80

70

60

50

40

30

20

10

0

Percent Ground Shading

Percen

t of M

ature ETc

32



EQuATIOn 2 CROP wATER uSE, InCHES PER DAy:

Crop Water Use, ETc (inches) = ETo x Kc x Crop Coverage Factor

Example

The ETo in mid June in central California is .35" per day. The crop is almonds, which has a Kc of .95 during this time of year. The orchard canopy covers 80% of the total orchard surface area. What is the crop water use (ETc) per day?

In some areas, ETc (crop ET) information is made available based on modeling average cropping situations, thus eliminating the need to track ETo and Kc information. The chart on the following page shows such ETc rates for drip-irrigated crops in Central California (Burt, 2007). Note that precipitation and reference ETo data are also supplied on the top two lines, whereas the rest of the data is pre-estimated crop ET.

Equation 2 Crop Water Use (in./day) Equation 2 Crop Water Use (in./day)

ETo x Kc x Crop Coverage = Crop Water Use, ETcExample: 0.35 in./day x 0.95 x 1.00 = 0.33 in./day


Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Annual

Precipitation 6.8 0.3 1.3 0.2 0.2 0.2 0.1 0.3 0.1 0.6 4.2 2.1 16.5

Grass Reference ETo 0.7 2.1 4.0 5.6 7.3 7.6 8.0 6.8 5.4 3.5 1.1 1.0 53.0

Apples, Pears, Cherries,Plums and Prunes 0.8 0.9 1.6 2.3 6.5 7.3 7.6 6.5 4.9 2.3 0.5 1.0 42.1

Apples, Plums, Cherries,etc., with Cover Crop 0.8 2.4 4.1 4.9 7.9 9.0 9.5 8.0 6.1 3.5 0.9 1.2 58.2

Peaches, Nectarines, and Apricots 0.8 0.9 1.6 2.2 6.0 6.8 7.2 6.2 4.6 2.2 0.5 1.0 40.1

Immature Peaches, Nectarines, etc. 0.8 0.9 1.3 1.2 3.5 4.0 4.2 3.7 2.6 1.6 0.5 1.0 25.3

Almonds 0.8 1.0 1.8 3.0 6.5 7.0 7.3 6.2 4.7 3.1 0.5 1.0 42.7

Almonds with Cover Crop 0.8 2.1 3.5 4.9 7.6 8.1 8.4 7.3 5.5 3.2 0.9 1.2 53.5

Immature Almonds 0.8 1.0 1.6 2.0 4.0 4.2 4.3 3.9 2.8 2.0 0.5 1.0 27.9

Walnuts 0.8 0.9 1.7 1.8 5.8 8..3 8.7 7.4 5.2 2.6 0.5 1.0 44.7

Pistachios 0.8 0.9 1.1 1.1 2.7 6.0 8.5 7.4 5.4 2.8 0.5 1.0 38.2

Pistachios with Cover Crop 0.8 2.1 3.4 3.7 5.3 7.3 9.0 7.7 5.9 3.6 0.9 1.2 50.8

Immature Pistachios 0.8 0.9 1.1 0.7 1.5 3.7 5.1 4.6 3.3 1.8 0.5 1.0 25.0

Miscellaneous Deciduous 0.8 0.9 1.6 2.3 6.2 6.8 7.2 6.3 4.7 2.2 0.5 1.0 40.4

Cotton 0.9 0.9 1.1 1.0 1.7 4.7 8.4 7.4 5.0 1.4 0.5 1.0 33.9

Miscellaneous Field Crops 0.9 0.9 2.2 1.4 2.6 7.1 7.7 3.1 0.1 0.6 0.5 1.0 28.0

Small Vegetables 0.9 1.5 3.6 5.5 1.6 0.2 0.2 1.4 1.3 1.3 0.8 1.2 19.5

Tomatoes and Peppers 0.9 0.9 1.7 0.8 3.7 8.0 7.3 1.2 0.1 0.6 0.5 1.0 26.4

Potatoes, Sugar Beets,Turnips, etc. 0.9 1.2 2.6 5.6 7.8 8.1 7.2 0.4 0.1 0.6 0.5 1.0 35.9

Melons, Squash, andCucumbers 0.9 0.9 1.1 0.2 1.0 1.0 4.2 4.9 1.5 0.6 0.5 1.0 17.8

Onions and Garlic 0.9 2.1 3.7 4.8 5.2 1.3 0.2 0.3 0.1 0.6 1.0 1.0 21.2

Strawberries 0.9 0.9 2.2 1.4 2.6 7.1 7.7 3.1 0.1 0.6 0.5 1.0 28.0

Flowers, Nursery, andChristmas Trees 0.8 0.9 1.6 2.3 6.2 6.8 7.2 6.3 4.7 2.2 0.5 1.0 40.4

Citrus without Ground Cover 0.8 2.2 3.5 3.9 4.8 5.1 5.2 4.6 3.5 2.8 0.9 1.2 38.4

Immature Citrus 0.9 1.6 2.5 2.2 3.0 3.1 3.2 2.9 2.1 1.9 0.7 1.1 25.1

Avocado 0.8 0.9 1.6 2.3 6.2 6.8 7.2 6.3 4.7 2.2 0.5 1.0 40.4

Miscellaneous Subtropical 0.8 0.9 1.6 2.3 6.2 6.8 7.2 6.3 4.7 2.2 0.5 1.0 40.4

Grapes 0.8 0.9 1.3 1.1 3.5 6.0 6.4 5.1 2.8 0.6 0.5 1.0 30.0

Grapes with Cover Crop 0.9 2.0 3.2 3.1 5.2 6.8 7.2 5.8 3.4 2.1 0.7 1.2 41.5

Immature Grapes 0.9 0.9 1.2 0.8 2.3 3.7 3.8 3.2 1.7 0.6 0.5 1.0 20.7

(Values shown in inches)

Typical Precipitation and Crop ET Values (ETc) for Drip Irrigated Crops in the San Joaquin Valley, CATypical Precipitation and Crop ET Values (ETc) for Drip Irrigated Crops in the San Joaquin Valley, CA

34



EQuATIOn 3 CROP wATER uSE, gALLOnS PER PLAnT:

In some cases, you may wish to convert crop water use data from inches to gallons per plant. In this case, the following formula should be used:

Crop Water Use (gallons/plant) = Crop Water Use, Inches/Day x .623 x Row Spacing, ft. x Plant Spacing, ft.

Example

The almond orchard mentioned above was planted on a 20 ft. x 20 ft. spacing. How many gallons of water are used per tree per day?

As youd expect, crop water use changes with weather and stage of crop growth. The figure at right shows a theoretical crop water use curve for cotton, in inches per day, in graphic form throughout the year.

Equation 3 Crop Water Use (gallons/plant) Equation 3 Crop Water Use (gallons/plant) Equation 3 Crop Water Use (gallons/plant)

Crop Water Use x .623 x Row Spacing x Plant Spacing = Gallons/PlantExample: 0.33 in./day x .623 x 20 ft. x 20 ft. = 82.2 gallons

Crop Water Use Curve for Cotton Crop Water Use Curve for Cotton

20 40 60 80 100 120 140 160 180 200

Water Use per Day (in.)

Water Use per Day (in.)

Days from SowingDays from Sowing

.08

.12

.16

.20

.23

.28

.31

.35

Apr May July Aug Sept OctJun

.08 .11.08 .11.11 .16.11 .16

.16 .33 .16 .33

.33 .19.33 .19

FinalEmergance

FirstSquare

FirstFlower

First Open Boll

Last Eective Flower

Pre-harvestPeriod


EQuATIOnS 4a AnD 4b: IRRIgATIOn SySTEM APPLICATIOn RATE

The drip system application rate, dependent on emission device flow rates and the spacing at which theyre placed, is defined as the volume of water applied to a surface area, and is usually stated in inches per hour. Equations 4a and 4b calculate application rates for tape with tape lateral spacing units in inches or feet respectively, while Equation 5 calculates application rates for on-line emitter, dripline, microjet, microspray and microsprinkler systems. Once the application rate is known, it must be de-rated by the drip system emission uniformity using Equation 6 to calculate a net application rate.

EQuATIOn 4a DRIP TAPE APPLICATIOn RATE, InCHES PER HOuR

(Lateral spacing in inches)Application Rate (inches/hr.) = (Q-100 x 11.6) / Tape Lateral Spacing, inches

Where: Q100 = Aqua-Traxx tape flow rate in GPM/100 ft. Lateral Spacing = Spacing between tape lines, inches

Example

Drip tape is being used to grow peppers. The flow is .34 gpm/100 ft., and the laterals are spaced 42 inches apart. What is the application rate?

EQuATIOn 4b DRIP TAPE APPLICATIOn RATE, InCHES PER HOuR

(Lateral spacing in feet)Application Rate (inches/hr.) = (Q-100 x .96) / Tape Lateral Spacing, feet

Where: Q100 = Aqua-Traxx tape flow rate in GPM/100 ft. Lateral Spacing = Spacing between tape lines, feet

Q-100 Drip Tape x 11.6 Lateral = Application Spacing (in.) Rate (in./hr.)

Example: 0.34 gpm/100 ft. x 11.6 42 in. = 0.09 in./hr.

Equation 4a Drip Tape Application Rate , in./hr. (lateral spacing in inches)Equation 4a Drip Tape Application Rate , in./hr. (lateral spacing in inches)

36



Example

Drip tape is being used to grow peppers. The flow is .34 gpm/100 ft., and the laterals are spaced 3.5 feet apart. What is the application rate?

Online Calculator Available

Note that users of Aqua-Traxx Premium Drip Tape may calculate application rates and run times using Toros online Aqua-Traxx Irrigation Calculator at www.toromicroirrigation.com or www.dripirrigation.org. Once the Aqua-Traxx model is chosen and the system pressure, lateral spacing and emission uniformity are entered, the calculator will present the system application rate along with the hours to apply 1.0 inch of water and 0.1 inches of water.

EQuATIOn 5 MICRO-IRRIgATIOn DEvICE APPLICATIOn RATE, InCHES PER HOuR

Equation 5 calculates the application rate in inches per hour for systems utilizing micro-irrigation devices such as on-line emitters, dripline, jets or microsprinklers. These devices are typically, but not always, used on permanent crops.

Application Rate (inches/hr.) = (Emission Device Flow Rate, gph x 1.6) / (Row Spacing, feet. x Device Spacing, feet)

Where: Emission Device Flow Rate = Flow rate of each emitter or jet or microsprinkler, stated in gph per device Row Spacing = Spacing between lateral lines of hose or dripline, feet Device Spacing = Spacing between emission devices along the lateral, feet

Q-100 Drip Tape x 0.96 Lateral = Application Spacing (ft.) Rate (in./hr.)

Example: 0.34 gpm /100 ft. x 0.96 3.5 ft. = 0.09 in./hr.

Equation 4b Drip Tape Application Rate, in./hr. (lateral spacing in feet)Equation 4b Drip Tape Application Rate, in./hr. (lateral spacing in feet)

Aqua-Traxx Irrigation Calculator1. Choose Aqua-Traxx Model

Aqua-Traxx Aqua-Traxx PC

Part Number:EAXxx0817, 8" spacing, 0.07 gph, 0.17 gpm/100'

Part Number Emitter Outlet spacing, inchesNominal emittter

flow, gphNominal gpm/100'

EAXxx0817 8 0.07 0.17

2. Enter Tape Inlet Pressure (PSI): 10 PSI Calculated Flow Rates: 0.08 gph/emitter 0.2 gpm/100'

3. Enter Spacing Between Tape Lateral Rows 3.5 feet inches

Calculated Gross Application Rate: 0.05 inches/hour

4. Enter Drip System Emission Uniformity: 90 % Calculated Net Application Rate: 0.05 inches/hour

Calculated Hours to apply 1.0 inch of water: 20.5

Calculated Hours to apply .10 inch of water: 2

Calculate ResetWelcome to Toro's Aqua-Traxx Irrigation Calculator! You can now easily calculate Tape Application Rate and Run Times at variable pressures. Just 1) Choose an Aqua-Traxx model and then 2) Enter Tape Inlet Pressure, 3) Tape Lateral Spacing, and 4) Drip System Emission Uniformity to see the answers. You can choose different Aqua-Traxx models and/or enter new data as often as you like.


Example

Dripline is being used to grow almond trees. The emitter flow rate is .60 gph and emitters are pre-inserted every 4 feet. The dripline rows are spaced 10 feet apart. What is the application rate?

Irrigation System net Application Rate

Now that the application rate is known, it must be de-rated by the irrigation systems uniformity to calculate net application rate. The system uniformity tells how evenly water is applied throughout the field and indicates how much over-irrigation must occur to ensure the driest part of the field receives enough water, i.e., how much over-irrigation will be required to compensate for imperfect uniformity. The system designer provides the theoretical uniformity, however, the actual uniformity of an exiting system may be determined

by taking flow measurements from a number of field emission devices, and then dividing the average measurement of the low quarter measurements (lowest 25% of the readings) by the overall average. Various terms are used by irrigation engineers to describe system uniformity, including distribution uniformity (DU) and emission uniformity (EU). The adjacent illustration, using Toros Color Traxx design software, visually maps flow variation (calculated using EU) in a drip design with color. Note that a design with an EU of 93.5% has less color variation, or flow variation, than a design with a lower, less desirable EU of 88.6%.

One of the main advantages of drip irrigation is the opportunity to obtain high system uniformity. In general, drip irrigation systems often achieve over 90% uniformity with proper design, installation and maintenance. This is in contrast to typical uniformities of 40-60% for gravity systems and 50-75% for sprinkler systems.

To determine the net application rate, simply multiply the application rate by the emission uniformity as shown in EQUATION 6 as follows.

Equation 5 Micro-irrigation Device Application Rate (in./hr.)Equation 5 Micro-irrigation Device Application Rate (in./hr.)

Emission Device x 1.6 Row x Device = ApplicationFlow (gph) Spacing (ft.) Spacing (ft.) Rate (in./hr.)Example: 0.6 gph x 1.6 10 ft. x 4 ft. = 0.024 in./hr.

"21 FH "8/5 - rehtO5421xx5PAE - oroT

93.5% EU 88.6% EU

isp 0.21 ,mpg 891isp 0.21 ,mpg 391

rh/ni 601.0 ,ca/mpg 0.84rh/ni 301.0 ,ca/mpg 8.64

300' manifold

Block: 4.13 acres, (600' lateral X 300' manifold)Manifold: Oval Hose, 300' @ 21 PSI, 4"

< -20

-15 to -20

-10 to -15

-5 to -10

62% 0 to -5

28% 0 to 5

10% 5 to 10

10 to 15

15 to 20

> 20

% Dev. from ave

47%

17%

10%

6%

10%

8%

2%

600'

Lat

eral

38



EQuATIOn 6 nET APPLICATIOn RATE (ALL TyPES OF SySTEMS)

Net Application Rate (inches/hr.) = Application Rate x Emission Uniformity

Example

The theoretical system application rate is .09 in./hr., and the emission uniformity was measured in the field to be 90%. What is the net application rate?

To help translate the importance of emission uniformity, the following illustrates how many hours are required to apply a minimum of 1.0 inch of water to all parts of an irrigated field assuming various emission uniformities and assuming an application rate of .09 inches per hour:

Thus, if the desired application rate is a minimum of 1.0 inch of water to all parts of the field, then the system must be run 12.3 hours if the system uniformity were 90%, whereas the system must be run for 13.9 hours if the system uniformity were 80%. Clearly, high system uniformities utilize time and resources more efficiently. In addition, high system uniformity often prevents runoff, deep percolation, fertilizer waste and over-irrigation to parts of the field and the resulting crop damage.

Equation 6 Net Application Rate - All System Types Equation 6 Net Application Rate - All System Types

Application Rate (in./hr.) x Emission Uniformity = Net Application Rate

Example: .09 in./hr. x .90 = .08 in./hr.

The Effect of System Uniformy on Hours to Apply One InchThe Effect of System Uniformy on Hours to Apply One Inch

Application Emission Net Application Hours to Apply Rate (inches) Uniformity Rate (inches) 1.0 Inches

0.09 0.95 0.086 11.70.09 0.90 0.081 12.3

0.09 0.80 0.072 13.9

0.09 0.70 0.063 15.9

0.09 0.60 0.054 18.5

0.09 0.50 0.045 22.2

High systemuniformity reducesoperating hours.


SuMMARy

Once the crop water use and the net application rate are known using Equations 2-6, a theoretical run time may be easily calculated using Equation 1.

Equation 1 Theoretical Run Time Per DayEquation 1 Theoretical Run Time Per Day

Crop Water Use Net Application Rate x 60 = Run Time Per DayExample: 0.33 in./day 0.08 in./hour x 60 = 248 minutes/day

Equation 2 Crop Water Use (in./day) Equation 2 Crop Water Use (in./day)

ETo x Kc x Crop Coverage = Crop Water Use, ETcExample: 0.35 in./day x 0.95 x 1.00 = 0.33 in./day

Equation 3 Crop Water Use (gallons/plant) Equation 3 Crop Water Use (gallons/plant) Equation 3 Crop Water Use (gallons/plant)

Crop Water Use x .623 x Row Spacing x Plant Spacing = Gallons/PlantExample: 0.33 in./day x .623 x 20 ft. x 20 ft. = 82.2 gallons

Equation 5 Micro-irrigation Device Application Rate (in./hr.)Equation 5 Micro-irrigation Device Application Rate (in./hr.)

Emission Device x 1.6 Row x Device = ApplicationFlow (gph) Spacing (ft.) Spacing (ft.) Rate (in./hr.)Example: 0.6 gph x 1.6 10 ft. x 4 ft. = 0.024 in./hr.

Equation 6 Net Application Rate - All System Types Equation 6 Net Application Rate - All System Types

Application Rate (in./hr.) x Emission Uniformity = Net Application Rate

Example: .09 in./hr. x .90 = .08 in./hr.

Q-100 Drip Tape x 11.6 Lateral = Application Spacing (in.) Rate (in./hr.)

Example: 0.34 gpm/100 ft. x 11.6 42 in. = 0.09 in./hr.

Equation 4a Drip Tape Application Rate , in./hr. (lateral spacing in inches)Equation 4a Drip Tape Application Rate , in./hr. (lateral spacing in inches)

Q-100 Drip Tape x 0.96 Lateral = Application Spacing (ft.) Rate (in./hr.)

Example: 0.34 gpm /100 ft. x 0.96 3.5 ft. = 0.09 in./hr.

Equation 4b Drip Tape Application Rate, in./hr. (lateral spacing in feet)Equation 4b Drip Tape Application Rate, in./hr. (lateral spacing in feet)

40


CHAPTER 3: Basic System Operation | 3.2-B Irrigation Scheduling: Additional Considerations

B. Additional Considerations Affecting the Irrigation ScheduleOnce theoretical run time is calculated, the irrigation manager must then adjust theory with real-world field conditions to decide how often to run the system to replenish each days withdrawals. This decision will depend on the Management Allowable Depletion (MAD) as well as other agronomic, cultural and weather related factors. The following Agricultural Irrigation Scheduling Table is an example of a full season schedule for tomatoes in central California based on average data from the Waterright scheduling tool (CIT, 2009).

These and other types of spreadsheet tools allow the user to input data on a daily or weekly basis regarding actual crop ET, application information, soil moisture data and/or crop data. The worksheet on the next page may be used on a daily basis to keep track of available water in the soil profile along with soil moisture readings.

Use online scheduling toolsto start, thenfine-tune.


In both of these examples note that soil texture, available water and soil moisture conditions must be known. Instruments are available to help determine these values, but simple field analysis is possible as well using readily available resources from government and academic sources. The following will discuss how Soil Texture, MAD, wetting patterns and the desire to avoid puddling influence the irrigation schedule beyond what the Water Balance Equations predict.

Soil Texture

Soil texture affects irrigation scheduling in two important ways. First, it determines how quickly the soil accepts water, and it should be known prior to design since it influences emission device flow rate and spacing. An application rate, or precipitation rate as its sometimes called, should have been chosen that does not exceed the soils ability to accept the water. Otherwise, runoff or puddling will occur. The adjacent Maximum Precipitation Rates table (USDA, 1997) shows that on heavier soils, runoff will occur with an application rate as low as .15 inches per hour. One of the advantages of drip irrigation systems is that application rates are often far below the maximum values shown in this chart, and pose less risk to create runoff than sprinkler systems, especially on bare, sloped ground.

Irrigation Scheduling Replace Whats Used TemplateIrrigation Scheduling Replace Whats Used Template

Field Zone Acres Soil Type Available Water/Foot Day Pump Pump Application Hours of Gross Water Net Water Crop ET Banked Water Net Water Soil Moisture Soil Moisture Soil Moisture Soil Moisture Pressure - Flow - Rate - Inches Operation Applied - Applied - Banked Status - Site 1 Status - Site 2 Status - Site 3 Status - Site 4 psi GPM Per Hour* Inches Inches** 1 50 400 0.09 6 0.53 0.48 0.20 0.28 0.28 2 50 400 0.09 0 0.00 0.00 0.25 -0.25 0.03 3 50 400 0.09 6 0.53 0.48 0.30 0.18 0.20 4 50 400 0.09 4 0.35 0.32 0.30 0.02 0.22 5 50 400 0.09 0 0.00 0.00 0.25 -0.25 -0.03 6 50 400 0.09 6 0.53 0.48 0.30 0.18 0.15 7 50 400 0.09 6 0.53 0.48 0.35 0.13 0.28 8 50 400 0.09 4 0.35 0.32 0.40 -0.08 0.20 9 50 400 0.09 6 0.53 0.48 0.40 0.08 0.27 10 50 400 0.09 6 0.53 0.48 0.35 0.13 0.40 11 50 400 0.09 0 0.00 0.00 0.30 -0.30 0.10 12 50 400 0.09 6 0.53 0.48 0.30 0.18 0.28 13 50 400 0.09 0 0.00 0.00 0.30 -0.30 -0.02 14 50 400 0.09 6 0.53 0.48 0.20 0.28 0.25

*Inches per hour = Pump ow, GPM x .0022 / Acres Serviced. **Net Water Applied = Gross water applied (inches) x 0.9 application eciency.

west 1 10 sandy loam 1.5 inches

Maximum Precipitation Rates* Maximum Precipitation Rates*

Coarse sandy

Uniform silt loams

Uniform light sandy loam

Heavy clay orclay loam

Silt loams over compact soil

Light sandy loamsover compact subsoil

Soil Coverage

Soil Composition

05% Slope 58% 812% 12%+

Covered Bare Covered Bare Covered Bare Covered Bare

1.75 1.50 1.25 1.00 1.00 0.75 0.75 0.40

2.00 2.00 2.00 1.50 1.50 1.00 1.00 0.50

1.75 1.00 1.25 0.80 1.00 0.60 0.75 0.40

1.25 0.75 1.00 0.50 0.75 0.40 0.50 0.30

0.60 0.30 0.50 0.25 0.40 0.15 0.30 0.10

0.20 0.15 0.15 0.10 0.12 0.08 0.10 0.06

1.00 0.50 0.80 0.40 0.60 0.30 0.40 0.20

Coarse sandy soilsover compact subsoil

* The maximum PR values, listed in inches/hour, are suggested by the United States Department of Agriculture. The values are average and may vary with respect to actual soil and ground cover conditions.

42



Second, soil texture determines how much water the root zone water reservoir holds per foot, and how much of that water is available to the plant. The adjacent illustration shows three levels of soil moisture: saturation, field capacity and wilting point. Much of the water in a saturated field will be lost to gravity and cannot be used for plant growth. After about 24 hours, the soil will achieve field capacity where water is available for plant use. At the wilting point, water is still present in the soil, but is held so tightly by the soil particles that its unavailable for plant use. The difference between field capacity and wilting point is considered water that is available to the plant. This is the soil moisture that growers manage to optimize crop production.

The adjacent Available Soil Moisture chart (Plaster, 2003) shows the range of moisture, in inches, that is potentially available to plant roots for different soil textures. Note that a sandy soil only has about .5 1.0 inches of available water per foot of depth, whereas a loam or silt loam has as much as 2.0 to 2.8 inches of available water per foot of depth.

This is further illustrated in the adjacent graph (Plaster, 2003). Soils that have limited available water must be managed very carefully because if crop water use cannot be replaced on a daily basis, if crops are shallow rooted, and/or if crop water usage is high, available water could become depleted and plants could wilt, possibly permanently. Irrigators must manage the available water in the root zone so that optimal crop production is achieved.

Soil texture many be determined by evaluating a tablespoon of soil with the palm of the hand and comparing it with information in the Soil Texture Identification Key (Thien, 1979) on the next page. Once texture is known, potential available water may be estimated using the table above. Soil Texture may also be determined by comparing the results of a Sedimentation Test with the Soil Texture Triangle (www.soilsensor.com) shown on page 44 (see Appendix for procedure). To determine actual moisture status of a known texture, the Feel Method may be used as illustrated in the table titled Soil Moisture, Feel and Appearance Description (USDA, 1998) on page 44. Pictures of a Fine Sand and Loamy Fine Sand are included to illustrate.

Soil Water ContentSoil Water Content

100 g 40 ml

20 ml

10 ml

8 ml

100 g

100 g

100 g Air

Air

Air

Solid

Pore SpaceSolid

Water

Saturation

SaturatedSoil

FieldCapacity

Wilting Coecient

HygroscopicCoecient

Field Capacity Wilting Point

Available Soil MoistureAvailable Soil Moisture

Coarse sand and gravel 0.02 0.06 0.2 0.7

Sand 0.04 0.09 0.5 1.1

Loamy sand 0.06 0.12 0.7 1.4

Sandy loam 0.11 0.15 1.3 1.8

Fine sandy loam 0.14 0.18 1.7 2.2

Loam and silt loam 0.17 0.23 2.0 2.8

Clay loam 0.14 0.21 1.7 2.5

Silty clay loam 0.14 0.21 1.7 2.5

Silty clay and clay 0.13 0.18 1.6 2.2

Soil Texture Inches per Inch Inches per Foot

The Eect of Soil Texture on Available WaterThe Eect of Soil Texture on Available Water

Fine Sandy Loam Silt ClaySand Loam Loam

Inch

es/Foo

t

0

1

2

3

4

(A)

(B)

Available Water

Unavailable Water

Gravitational Water


Soil Texture Identication KeySoil Texture Identication Key

Place approximately 25 g of soil in palm. Add water by the drop and knead the soil to break down all aggregates. Soil is at the proper consistency when plastic and moldable, like moist putty.

Sand

Loam Clay

SiltLoam

LoamySand

SandyLoam

ClayLoam

SandyClay

Silty Clay

SandyClayLoam

SiltyClayLoam

Place ball of soil between thumb and forefinger, gently pushing soil with thumb, squeezing it upward into a ribbon. Form a ribbon of uniform thickness and width. Allow ribbon to emerge and extend over forefinger, breaking from its own weight.

Excessively wet a small pinch of soil in palm and rub with forefinger.

Add dry soil to soak up the water.

Is soil too dry?

Does soil form a ribbon?

Does soil feel very gritty?



Does soil feel very smooth?



Neither grittiness nor smoothness predominates.

Is soil too wet?Does soil remain in a ball when squeezed.

Does soil make a weak ribbon less than 2.5 cm longbefore breaking?

Does soil make a medium ribbon2.55 cm long before breaking?

Does soil make astrong ribbon 5 cm or longer before breaking?



Yes

Yes Yes Yes

Yes

Yes

YesYesYes

Yes

START

No

No

No No No

Yes Yes Yes

No No No

Yes Yes Yes

No

No

No No

44



Management Allowable Depletion (MAD)

MAD is a term that describes how much of the available water is allowed to deplete before its replaced with irrigation. This is largely an agronomic decision because water availability is often used to manipulate crop growth and quality. In some cases, a full reservoir is desired and water is replaced as it is depleted as discussed in the Water Balance Method. In other cases, some level of plant water stress may be desired and maintained via the irrigation schedule. In any case, the Water Balance Method may be used to manage the soil water reservoir. The scheduler must simply determine whether the reservoir is to be kept full or depleted to some level.

Sometimes MAD is dictated by system or cultural logistics. It may be inconvenient or impossible to fill the soil reservoir on every block each day, or cultural activities may prohibit irrigation. However, using drip often eliminates these issues, because:

Drip application rates are low, so more acres may be irrigated at once.

Drip systems typically apply water to the crop root zone and/or beds only and leave furrows and drive roads dry, allowing irrigation to occur even when field operations (including harvest) are taking place.

Since nutrients are often applied through the drip system, tractor applications can be minimized or even eliminated.

In summary, agronomic reasons rather than logistics usually dictate the drip schedule.

4

Appearance of sandy clay loam, loam, and silt loam soilsat various soil moisture conditions.Available WaterCapacity1.5-2.1 inches/footPercent Available: Currently available soil mois-ture as a percent of available water capacity.In/ft. Depleted: Inches of water currently needed torefill a foot of soil to field capacity.0-25 percent available2.1-1.1 in./ft. depletedDry, soil aggregations break away easily, no stain-ing on fingers, clods crumble with applied pressure.(Not pictured)

25-50 percent available1.6-0.8 in./ft. depletedSlightly moist, forms a weak ball with rough sur-faces, no water staining on fingers, few aggregatedsoil grains break away.

50-75 percent available1.1-0.4 in./ft. depletedMoist, forms a ball, very light staining on fingers,darkened color, pliable, forms a weak ribbon be-tween the thumb and forefinger.

75-100 percent available0.5-0.0 in/ft. depletedWet, forms a ball with well-defined finger marks,light to heavy soil/water coating on fingers, ribbonsbetween thumb and forefinger.100 percent available0.0 in/ft. depleted (field capacity)Wet, forms a soft ball, free water appears briefly onsoil surface after squeezing or shaking, medium toheavy soil/water coating on fingers. (Not pictured)

4




75-100 percent available0.5-0.0 in/ft. depletedWet, forms a ball with well-defined finger marks,light to heavy soil/water coating on fingers, ribbonsbetween thumb and forefinger.100 percent available0.0 in/ft. depleted (field capacity)Wet, forms a soft ball, free water appears briefly onsoil surface after squeezing or shaking, medium toheavy soil/water coating on fingers. (Not pictured)4




75-100 percent available0.5-0.0 in/ft. depletedWet, forms a ball with well-defined finger marks,light to heavy soil/water coating on fingers, ribbonsbetween thumb and forefinger.100 percent available0.0 in/ft. depleted (field capacity)Wet, forms a soft ball, free water appears briefly onsoil surface after squeezing or shaking, medium toheavy soil/water coating on fingers. (Not pictured)

Soil Moisture, Feel and Appearance DescriptionsSoil Moisture, Feel and Appearance Descriptions

Sand Sandy Loam Loam/Silt Loam Clay Loam/ClayWater * Available

Above eld capacity

100% (eld

capacity)

75100%

5075%

2550%

025%

Free water appears when soil is bounced in hand.

Upon squeezing, no free water appears on soil, but wet outline of ball is left on hand. (1.0)

Tends to stick together slightly, sometimes formsa weak ball with pressure. (0.81.0)

Appears to be dry, will not form a ball with pressure. (0.50.8)

Appears to be dry, will not form a ball with pressure. (0.20.5)

Dry, loose, single- grained flows through fingers. (00.2)

Free water is released with kneading.

Appears very dark. Upon squeezing, no free water appears on soil, but wet outline of ball is left on hand. (1.5)

Quite dark. Forms weak ball, breaks easily. Will not stick. (1.2 1.5)

Fairly dark. Tends to form a ball with pressure, but seldom holds together. (0.81.2)

Light colored. Appears to be dry, will not form a ball. (0.40.8)

Very slight color. Dry, looseflows through fingers. (00.4)

Free water can be squeezed out.

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